The present invention relates, in general, to semiconductor devices and, more particularly, to low noise amplifiers.
Generally, communications systems transfer information from a source to a destination using a combination of a transmitter and a receiver. Typically, the transmitter includes a transducer and a transmission element which together convert an electrical signal into an electromagnetic signal. The electromagnetic signal is then transmitted through a transmission medium to the receiver, which converts it into a desired form for a use by an end user. The transmission medium may be a copper cable, an optical fiber, air, etc.
The receiver portion of the communications system typically includes a low noise amplifier, a local oscillator, a mixer circuit, and an intermediate frequency (IF) amplifier coupled to an output of the receiver via a detector circuit. Most low-noise amplifiers are included in the receiver portion to optimize the noise figure of the receiver. These amplifiers usually have two or more gain stages as well as impedance matching networks. Preferably, the first stage is designed to have a low noise figure at a moderate gain and the second stage is designed to have a high gain at a moderate noise figure. A drawback of this type of design is that it limits the dynamic range or maximum receivable signal of the receiver.
Accordingly, it would be advantageous to have a method and a circuit for extending the dynamic range of a receiver system. It would be of further advantage for the method and circuit to be cost efficient and manufacturable using common semiconductor processing techniques.